anatomy of the abdominal wall and peritoneum

Question 1

what are the borders of the abdominal wall?

Answer 1

superior - the xiphoid process of the sternum & coastal cartilages

inferior - iliac crest & public bones of the pelvis

anterior - the abdominal muscles

posterior - the spine

Question 2

what are the lines dividing the abdominal area?

Answer 2

midclavicular x2
transpyloric plane
inter-tubercular plane

Question 3

what are the 9 abdominal regions?

Answer 3

TOP 1/3
right hypochondriac, epigastric, left hypochondriac

MID 1/3
right lumbar/flank, umbilical, left lumbar/flank

BOTTOM 1/3
right iliac, hypogastric/suprapubic, left iliac

Question 4

where is the transpyloric plane (of Addison)

Answer 4

• Midway between the pubic synthesis and the jugular notch
• Runs from the tip of the 9th costal cartilage
• at approximately the level of L1 vertebral body
• it is the point where the midclavicular line crosses the costal margin?

Question 5

where is McBurney’s point?

Answer 5

• between the umbilicus and the anterior superior iliac spine (ASIS) on right side
• it lies 2 thirds of the way along this line, over the iliac fossa.
• It is where the base of the appendix usually lies (tender in acute appendicitis)

Question 6

what are the 4 layers of the abdominal wall?

Answer 6

• Skin
• Superficial fascia: Fatty connective tissue
• Muscles and associated fascia
• Parietal peritoneum

Question 7

how many Anterior abdominal wall muscles are there?

Answer 7

• 3 Pairs of flat muscles

- 2 pairs of vertical muscles

Question 8

name the 3 flat muscles of the anterior abdominal wall?

Answer 8

• external oblique
• internal oblique
• transversus abdominis

Question 9

where does the external oblique originate and insert?

Answer 9

originates from lower ribs (5-12)

insertions

• iliac crest
• pubic bone (crest, symphysis, tubercle)
• becomes aponeruiosis ( xiphoid process and the linea alba)

Question 10

what are the functions of the external and internal obliques?

Answer 10

1. Contralateral rotation of the torso.
2. flexion of the trunk

• Bilateral contraction of EO, rectus abdominis and IO - this flexes the trunk by drawing the pubis towards the xiphoid (like in crunches or sit-ups)

Question 11

where does the internal oblique originate and insert?

Answer 11

ORIGINS:

• the inguinal ligament,
• iliac crest
• the lumbodorsal fascia

INSERTIONS:

• ribs 10-12,
• costal cartilages,
• becomes Aponeurosis: Xiphoid process, pubic tubercle, linea alba, pubic synthesis

Question 12

which of the flat muscles is deepest? which is largest?

Answer 12

EO - largest
IO - deep to EO, smaller and thinner
transversus abdominis - deepest

Question 13

what direction to each of the flat muscles fibres run?

Answer 13

EO - ‘hands in pockets’ inferomedially
IO - superomedially, perpendicular to EO
transversus abdominis - horizontally

Question 14

what is the innervation of the flat muscles?

Answer 14

• Thoracoabdominal nerves (T7-T11)
• subcostal nerve (T12).

IO and transversus abdominis:
- additionally innervated by branches of the lumbar plexus.

Question 15

what is the function of the transversus abdominis?

Answer 15

Compression of abdominal contents.

Question 16

what are the origins and insertions of the transversus abdominis?

Answer 16

origins - the inguinal ligament, costal cartilages 7-12, the iliac crest and thoracolumbar fascia.

insertions - the conjoint tendon. Aponeurosis: Xiphoid process, pubic tubercle, linea alba, pubic synthesis

Question 17

what is the aponeurosis in the anterior abdominal wall?

Answer 17

• each flat muscle forms an aponeurosis (broad flat tendon tissue that anchors muscles) near to midclavicular line
• aponeurosis of each flat muscles connects with its pair on other side of midline
• the aponeurosis covers the vertical rectus abdominis muscle

Question 18

what is the white central line extending from the xiphoid process of the sternum to the pubic symphysis called? what is it made of?

Answer 18

• the linea alba
• a fibrous structure
• formed from the aponeuroses of all the flat muscles where they meet in the midline

Question 19

name the 2 vertical muscles

Answer 19

1. rectus abdominis

2. pyramidalis

Question 20

what are the origins and insertions of the rectus abdominis?

Answer 20

origins - pubic crest

insertions - xiphoid process, costal cartilage of ribs 5-7

Question 21

what are the origins and insertions of the pyramidalis?

Answer 21

origins - pubic crest and pubic symphysis

insertions - the linea alba

Question 22

what is the function of the rectus abdominis?

Answer 22

• compressing the abdominal viscera,
• stabilises the pelvis during walking,
• depresses the ribs

Question 23

what is the function of the pyramidalis?

Answer 23

to tense the linea alba.

Question 24

what is the innervation for the vertical muscles?

Answer 24

rectus abdominis - Thoracoabdominal nerves (T7-T11).

pyramidalis - Subcostal nerve (T12).

Question 25

which is the bigger of the vertical muscles? describe their shapes?

Answer 25

rectus abdominis - long, paired muscle, found either side of the midline in the abdominal wall pyramidalis- small triangular muscle, found superficially to the rectus abdominis.

Question 26

what is the linea semilunaris?

Answer 26

surface marking created by the lateral borders of the rectus abdominis muscles

Question 27

what is the blood supply to the vertical muscles?

Answer 27

Inferior epigastric arteries (+ superior for pyramidalis)

Question 28

what makes up the '6 pack'?

Answer 28

The rectus abdominis muscle, the tendinous intersections of this muscle, and the linea alba

Question 29

what muscles is the rectus sheath formed from?

Answer 29

the aponeuroses of the 3 flat muscles (EO,IO,transversus abdominis)

Question 30

what muscles does the rectus sheath enclose?

Answer 30

the 2 vertical muscles ( rectus abdominis, pyramidalis)

Question 31

describe the rectus sheath layers in the upper 2/3 of the abdomen?

Answer 31

The anterior wall - is formed by the aponeuroses of the external oblique, and of half of the internal oblique. (1.5 layers) The posterior wall- is formed by the aponeuroses of half the internal oblique and of the transversus abdominis. (1.5 layers) anterior/posterior to rectus abdominis muscle (enclosed)

Question 32

describe the rectus sheath layers in the lower 1/3 of the abdomen?

Answer 32

anterior wall - formed by all the aponeuroses (EO,IO,transversus abdominis) posterior wall - none (in direct contact with the transversalis fascia)

Question 33

what line divides the upper 2/3 from the lower 1/3 of the abdomen?

Answer 33

the arcuate line - Approximately midway between the umbilicus and the pubic symphysis

Question 34

what arteries supply the abdominal wall?

Answer 34

- epigastric (sup + inf) - segmental lumbar arteries - Intercostal arteries

Question 35

what veins drain the abdominal wall?

Answer 35

- Intercostal veins drain into the azygos system - Lumbar veins drain to the veins of the posterior abdominal wall and the azygos system - Superior and inferior epigastric veins drain to subclavian and femoral veins respectively

Question 36

what is the peritoneum?

Answer 36

a continuous membrane which lines the abdominal cavity and covers the abdominal organs

Question 37

what is the role of the peritoneum?

Answer 37

- support the viscera/organs | - provides pathways for blood vessels and lymph to travel to and from the viscera.

Question 38

what are the 2 layers to the peritoneum?

Answer 38

- visceral (lines the organs) | - parietal (lines the wall)

Question 39

what epithelium lines the peritoneum?

Answer 39

- simple squamous epithelial cells - called mesothelium - same for both layers

Question 40

what derived the 2 layers of the peritoneum in the embryo?

Answer 40

pariteal - somatic mesoderm visceral - splanchnic mesoderm

Question 41

what is the nerve supply of the parietal peritoneum? how does this affect pain sensation?

Answer 41

- same somatic nerve supply as the region of the abdominal wall is lines - so well localised pain

Question 42

what is the nerve supply of the visceral peritoneum? how does this affect pain sensation?

Answer 42

has the same autonomic nerve supply as the viscera it covers - pain is poorly localised - pain is referred to dermatomes

Question 43

what are the 2 functions of the peritoneal cavity (potential space)?

Answer 43

- the peritoneal fluid acts as a lubricant to enable free movement of abdominal viscera/organs ] - contains antibodies to fight infection

Question 44

what are intraperitoneal organs? | give examples

Answer 44

- if they are enveloped by visceral peritoneum anteriorly and posteriorly eg. stomach,spleen,liver

Question 45

what are retroperitoneal organs?

Answer 45

- when organs are not covered in visceral peritoneum | - only parietal peritoneum on their anterior surface

Question 46

what is the difference between primary and secondary retroperitoneal organs?

Answer 46

primary - developed as retroperitoneal (oesophagus, rectum and kidneys) secondary - initially intraperitoneal (ascending and descending colon)

Question 47

what abdominal organs are retroperitoneal ?

Answer 47

SAD PUCKER ``` Suprarenal glans (adrenal) Aorta & IVC Duodenum Pancreas Ureters Colon (asc,desc) Kidneys Eosophagus Rectum ```

Question 48

what is a mesentery?

Answer 48

= double layer of visceral peritoneum

Question 49

what are the roles of the mesenteries?

Answer 49

connects intraperitoneal organs to posterior abdominal wall carries blood vessels, nerves, lymphatics absorbs nutrients

Question 50

what organ is the main mesentery connected to?

Answer 50

- the small intestine

Question 51

what is an omentum?

Answer 51

omenta = - sheets of visceral peritoneum - that extend from the stomach and proximal part of the duodenum to other abdominal organs.

Question 52

what is the role of the GREATER omentum? how many layers is it?

Answer 52

= 4 visceral peritoneum layers - attaches to GREATER curvature of stomach + proximal duodenum + transverse colon - migrates to infected viscera - contains lots of lymph's and vessels

Question 53

what is the role of the LESSER omentum? what are its attachments?

Answer 53

= a double layer of visceral peritoneum (smaller then great) - attaches from the lesser curvature of the stomach and the proximal part of the duodenum to the liver.

Question 54

what 2 ligaments does the lesser omentum contain?

Answer 54

1. the hepatogastric ligament (flat broad sheet) 2. the hepatoduodenal ligament (free edge)

Question 55

what important vessels does the lesser omentum contain? what organ do they supply?

Answer 55

the portal triad - hepatic artery - portal vein - bile dict within the hepatoduodenal ligament (the free edge) provides blood suppply to liver

Question 56

what is a peritoneal ligament?

Answer 56

- the double fold of peritoneum that connects the viscera to another viscera or the abdominal wall

Question 57

what is the falciform ligament?

Answer 57

- sickle shaped - attaches anterior surface of liver to anterior abdominal wall - its free edge contains the ligamentum teres

Question 58

what is the ligamentum teres ?

Answer 58

a remanent of the umbilical vein (oxygenated blood from placenta to fetus) on the free edge of the falciform ligament

Question 59

what is the urachus?

Answer 59

- fibrous cord | - remnant of a channel between the bladder and the umbilicus

Question 60

what is a dermatome?

Answer 60

- area of skin - which is supplied by the same sensory ganglia and spinal cord segments as the nerve fibres innervating the viscera eg. Irritation of the diaphragm (e.g. as a result of inflammation of the liver, gallbladder or duodenum) may result in shoulder tip pain.